Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.75	7.243%	$204.566	$204.57	$204.55	$204.60
Purchase #2	$50.28	7.815%	$54.2094	$54.21	$54.20	$54.20
Purchase #3	$166.42	13.380%	$188.687	$188.69	$188.70	$188.70
Purchase #4	$67.54	6.302%	$71.7964	$71.80	$71.80	$71.80
Purchase #5	$87.94	12.850%	$99.2403	$99.24	$99.25	$99.20
Purchase #6	$132.57	10.332%	$146.2671	$146.27	$146.25	$146.30
Purchase #7	$214.68	12.299%	$241.0835	$241.08	$241.10	$241.10
7 purchase totals =	$910.18		$1,005.8497	$1,005.86	$1,005.85	$1,005.90